Sliding sleeve connection

ABSTRACT

A sliding sleeve connection between an expanded end of an all-plastic pipe or of a plastic composite pipe and a connecting element includes an expanded end of an all-plastic pipe or of a plastic composite pipe; a connecting element having at least one support body provided with circumferential external ribs, onto which the expanded end of the all-plastic pipe or of the plastic composite pipe is slid, and at least one circumferential collar; and a sliding sleeve made of elastically deformable polymer material axially slid onto the expanded end. The connecting element includes a pre-stop between the circumferential collar and the nearest circumferential external rib to the latter. The pre-stop constitutes a limitation for sliding onto the end of the pipe. The end of the sliding sleeve facing the circumferential collar protrudes beyond the end of the pre-stop facing the circumferential external rib.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase application filed under 35U.S.C. § 371 of International Application No. PCT/EP2016/002132, filedDec. 19, 2016, designating the United States, which claims priority fromGerman Patent Application No. 20 2015 106 953.7 filed Dec. 21, 2015,which are hereby incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a sliding sleeve connection between anexpanded end of an all-plastic pipe or of a plastic composite pipe and aconnecting element, wherein the sliding sleeve connection comprises anexpanded end of an all-plastic pipe or of a plastic composite pipe, aconnecting element with at least one support body provided withcircumferential external ribs, onto which the expanded end of theall-plastic pipe or of the plastic composite pipe is slid or pushed, andat least one circumferential collar and a sliding sleeve made ofelastically deformable polymer material axially slid onto the expandedend.

Such sliding sleeve connections are known in the prior art. In additionto at least one end of an all-plastic pipe or of a plastic compositepipe, such a pipe connection comprises a connecting element with atleast one support body having circumferential external ribs, onto whichthe end of the pipe is slid. The end of the pipe is fixed to theconnecting element via a fixing sleeve arranged over the end of thepipe, through which the end of the pipe is pressed against the externalcontour of the support body provided with circumferential external ribs.Depending on how the fixing sleeve used is attached, a distinction ismade between various types of connecting techniques. In sliding sleeveconnections, also referred to as axial press-fit systems, the supportbody of the connecting element is inserted into an expanded end of apipe and a sliding sleeve attached externally to the end of the pipe ispress-fitted in an axial direction onto the end of the pipe withinserted support body of the connecting element by means of a specificsliding tool. Such an axial press-fitting system with a sliding sleeveis described in DE 101 30 858 A1, for example. The sliding sleevedescribed therein is made of an elastically deformable polymer material.The connecting element has a circumferential collar, which isencompassed by the sliding tool when the sliding sleeve is slid onto. Inorder to achieve an axial fixing of the sliding sleeve, the latter iselastically attached on both sides of the circumferential external ribsto the expanded end of the pipe, thereby creating a type of form fit,which holds the sliding sleeve in its axial position in the slidingsleeve connection. What is viewed as a disadvantage of the slidingsleeve connection described in DE 101 30 858 A1, is that when axiallypress-fitting the sliding sleeve, there is the risk of that the expandedend of the pipe is further displaced in the direction of thecircumferential collar, thereby leading to a weakening of the axialfixing of the sliding sleeve. By this, the risk of disconnecting thepipe connection is increased.

SUMMARY OF THE INVENTION

Therefore, it is the object of the present invention to provide asliding sleeve connection that overcomes the disadvantages of the priorart. In particular, the sliding sleeve connection according to theinvention is intended to have higher resistance and counter the tendencyto relative motion of the sliding sleeve on the expanded end of thepipe.

These and other objects are solved in accordance with the presentinvention.

According to the present invention, it has been found that the stabilityof the sliding sleeve connection can also be increased in that thesliding sleeve made of an elastically deformable material is bent in thefinal connection towards the support body on the side of the supportbody facing the circumferential collar. According to the invention, thisis achieved in that a pre-stop is provided between the circumferentialcollar and the nearest circumferential external rib to the latter. Thepre-stop constitutes a limitation in sliding onto the expanded end ofthe pipe in an axial direction. This causes a hollow space between thepre-stop and the circumferential collar, which can spatially accommodatethe section of the sliding sleeve bent towards the support body.

Accordingly, the present invention provides a sliding sleeve connectionbetween an expanded end of an all-plastic pipe or of a plastic compositepipe and a connecting element, comprising an expanded end of anall-plastic pipe or of a plastic composite pipe; a connecting elementhaving at least one support body provided with circumferential externalribs, onto which the expanded end of the all-plastic pipe or of theplastic composite pipe is slid, and at least one circumferential collar;and at least one sliding sleeve made of an elastically deformablepolymer material axially slid onto the expanded end, wherein theconnecting element between the circumferential collar and the nearestcircumferential external rib to the latter has a pre-stop, whichconstitutes a limitation for the sliding onto of the end of the pipe,wherein the end of the sliding sleeve facing the circumferential collarprojects beyond the edge of the pre-stop facing the circumferentialexternal ribs.

The term “length of the support body”, as used herein, means thedistance between an open end of a support body of the connecting elementand the edge of the circumferential collar facing the open end.Furthermore, the term “external diameter of the base area of the supportbody”, as used herein, means the double distance between a longitudinalaxis of a support body of the connecting element and the deepest pointof the relevant support body between the pre-stop and thecircumferential external rib adjacent to the latter.

It can also prove helpful if the circumferential collar is connectedwith the pre-stop via a plurality of bridges. Such connecting bridgesbetween the circumferential collar and the pre-stop provide theconnecting element with additional stability, as the forces acting onthe circumferential collar during the axial press-fitting of the slidingsleeve, which the corresponding sliding tool engages, are partiallydeflected to the pre-stop as well. In alternative embodiments of thepresent invention increased stability can also be achieved byconfiguring the pre-stop in a stepped arrangement to the circumferentialcollar as an integral component thereof.

Likewise, it can be useful if the distance between the edge of thepre-stop facing the circumferential external ribs and the edge of thecircumferential collar facing the pre-stop is 0.10 times to 0.30 timesthe length of the support body, in particular 0.12 times to 0.25 timesthe length of the support body and, preferably, 0.13 to 0.20 times thelength of the support body. A distance in this range has proved to besufficient to configure a bend of the sliding sleeve during theproduction of the sliding sleeve connection according to the invention,while maintaining the stability of the connecting element.

It might as well be favourable, if the external diameter of the pre-stopis 1.1 times to 1.5 times, preferably 1.15 times to 1.4 times andparticularly preferably 1.2 times to 1.3 times the external diameter ofthe circumferential external rib with the largest diameter. With anexternal diameter of the pre-stop within the stated range, the pre-stopconstitutes a sufficiently large obstacle for the pipe during axiallysliding onto of the sliding sleeve. A pre-stop with too large anexternal diameter outside the stated range would mean that the slidingsleeve in the sliding sleeve connection could attach itself to thepre-stop, thus not increasing the stability of the sliding sleeveconnection and possibly deteriorate it instead.

Furthermore, it can prove helpful if at least one of the circumferentialexternal ribs of the supporting body has a saw tooth cross section andat least one of the circumferential external ribs has a substantiallyrectangular cross section. The presence of a rectangular sealing ribcontributes to a secure sealing between the pipe and the connectingelement in the sliding sleeve connection according to the invention,while a saw tooth-shaped circumferential external rib in the slidingsleeve connection according to the invention effectively prevents theend of the pipe slipping off from the support body of the connectingelement. It is especially preferred in this context if at least onesaw-tooth-shaped circumferential rib, in particular all saw-tooth-shapedcircumferential ribs are arranged in such a way that the inclined sideof the saw tooth points in the direction of the open end of the supportbody. The support body, beginning at the open end thereof, preferablyhas two circumferential external ribs with saw-tooth-like cross sectionsand a circumferential external rib with rectangular cross section. Inalternative embodiments the support body, also beginning at the open endthereof, can also have a circumferential external rib withsaw-tooth-like cross-section, two circumferential external ribs withrectangular cross section and again a circumferential external rib withsaw-tooth-like cross section.

Likewise, it can be advantageous if the interval between two adjacentcircumferential external ribs, always measured from the edge thereoffacing the circumferential collar, is 0.10 to 0.5 times and particularlypreferably 0.20 times to 0.25 times the length of the support body. Adistance between two adjacent circumferential external ribs within thestated range allows the circumferential external ribs of the connectingelement to press into the end of the pipe press-fitted onto the pipeconnection section, wherein the distance determines a desireddistribution of a preferred number (in particular three or four) ofcircumferential external ribs on the support body of the connectingelement.

It can also be useful if the width of at least one of thecircumferential external ribs with a substantially rectangularcross-section is 0.01 to 0.08 times, particularly preferably 0.02 to0.06 times, the length of the support body. If the width of thecircumferential external ribs is within the stated range, thecircumferential external ribs of the connecting element can slide farenough with sufficient sealing effect into the end of the pipepress-fitted onto the support body as to ensure a secure fit of the endof the pipe on the support body of the connecting element.

It has also proven to be advantageous if the external diameter of eachindependent circumferential external rib equals 1.03 times to 1.3 timesthe external diameter of the base area of the support body. If theexternal diameter of the circumferential external ribs with relation tothe external diameter of the base area of the support body is within thestated range, sufficient tightness of the sliding sleeve connectionaccording to the invention is ensured with low material consumption forthe circumferential external ribs. In this regard, the external diameterof the circumferential external ribs is particularly preferred 1.05times to 1.2 times the external diameter of the base area of the supportbody, in particular 1.07 times to 1.1 times the external diameter of thebase area of the support body. The external diameter of acircumferential external rib with a saw-tooth-shaped cross sectionpreferably corresponds to the external diameter of a circumferentialexternal rib with rectangular cross section.

It can also be useful if the width of the circumferential collar equals0.050 times to 0.20 times the length of the support body, in particular0.060 times to 0.15 times the length of the support body and preferably0.070 times to 0.11 times the length of the support body. A width of thecircumferential collar offers sufficient force absorption when using thesliding sleeve tool with low material effort.

It can also be useful if the external diameter of the circumferentialcollar is 1.1 times to 2.0 times, in particular 1.1 times to 1.8 times,and preferably 1.2 times to 1.5 times the external diameter of thecircumferential external rib with the largest external diameter. If theexternal diameter of the circumferential collar is within this range,the risk of the press-fit tool slipping off the circumferential collarduring press-fitting is low, thus resulting in the resistance of thecircumferential collar.

It can also be preferred if the distance between the pre-stop of theconnecting element and the nearest circumferential external rib to thelatter equals 0.10 to 0.50 times, particularly preferred 0.20 times to0.36 times the length of the support body. With such a configuration ofthe distance between the pre-stop of the connecting element and anearest circumferential external rib to the latter, a region of thesupport body is created in which the end of the pipe press-fitted ontothe support body can partially assume the form of the bend of thesliding sleeve in the sliding sleeve connection according to theinvention, thus further increasing the stability of the sliding sleeveconnection according to the invention.

Likewise, it can be advantageous if the length of the support body is0.60 times to 2.0 times, in particular 0.90 times to 1.8 times, andpreferably 1.1 times to 1.5 times the external diameter of thecircumferential external rib with the largest diameter. If the length ofthe support body is within the stated range, the connecting element hasgood resilience to bending stress with reasonable material effort.

It can also be helpful if the ratio of the height of the pre-stop overthe base area of the support body to the wall thickness of the piperanges from 0.40 to 1.0, in particular from 0.50 to 0.98, and preferablyfrom 0.60 to 0.96. A relative height of the pre-stop enables pipes withdifferent wall thicknesses to be used in the sliding sleeve connectionaccording to the invention.

With regard to the pipe connection according to the invention, it may bepreferred if the following applies to the expansion ratio R(exp) of thepipe connection:0.05<R(exp)=[D(max)/D(internal)]−1<0.35wherein D(max) stands for the maximum external diameter of thecircumferential external ribs and D(internal) for the internal diameterof the pipe. If plastic pipes are used, an expansion ratio in this rangeis large enough to ensure sufficient tightness of the connection. Inaddition, if metal-plastic composite pipes are used, the expansion ratiois sufficiently small to prevent any damage of the metal layer of theMCV pipe due to a too strong local strain. This makes the connectingelement universally usable for all pipe wall strengths with the givenexternal diameter of the used pipe. Thereby, the number of stockpiledfittings for the plumber is reduced and the danger of confusion in theselection of fittings is decreased.

When using a plastic pipe, it is advantageous according to the inventionif the expansion ratio R(exp) of the pipe connection according to theinvention ranges from 0.10 to 0.35, particularly preferably from 0.15 to0.25. A sufficiently tight pipe connection is achieved if the expansionratio of the pipe connection according to the invention is within thisrange when using a plastic pipe, wherein no excessive effort is requiredwhen expanding the pipe.

When using a metal-plastic composite pipe, it has proved advantageouswith regard to an improved tightness of the pipe connection according tothe invention and an integrity of the metal layer contained in the pipeif the expansion ratio R(exp) of the pipe connection ranges from 0.05 to0.25 and particularly preferably from 0.10 to 0.20.

It is also preferred if the internal surface of the sliding sleeve hasan average roughness value R_(a) ranging from 1 μm to half of theaverage wall thickness of the sliding sleeve. An increased roughness onthe internal surface of the sliding sleeve, compared with the smoothinternal surfaces of sliding sleeves for axial slid-onto systemspreviously used according to the prior art, leads to a reduction in theforce needing to be exerted for axially-sliding the correspondingsliding sleeve onto the expanded end of the pipe with inserted supportbody. At the same time, an internal surface of the sliding sleeve withincreased roughness is accompanied by a lower tendency to relativemotion of the sliding sleeve on the expanded end of the pipe, inparticular in the event of thermal cycling. These two significantadvantages of the rough internal surface of the sliding sleeve are to beobserved as of an average roughness value R_(a) of the internal surfaceof the sliding sleeve of 1 μm. If this average roughness value R_(a) ofthe internal surface of the sliding sleeve exceeds half of the averagewall thickness of the sliding sleeve, it may occur that the slidingsleeve does not exert sufficient pressure on the expanded end of thepipe with the inserted support body of the connecting element. Thiscould lead to a less tight sliding sleeve connection. It can beadvantageous in this regard if the internal surface of the slidingsleeve has an average roughness value R_(a) ranging from 3 μm to 1000μm, preferably from 5 μm to 50 μm. The stated ranges of the averageroughness value achieve a particularly well-balanced ratio betweenreduced force to be exerted for press-fitting and sufficient stabilityof the resulting sliding sleeve connection according to the invention.The term “average roughness value” (designated by the symbol “R_(a)”) ofa surface, as used herein, means the arithmetic average or mean of theamount deviation of all measuring points on the surface from the centreline of the surface. Such effects can be alternatively or additionallyincreased or achieved if the internal surface of the sliding sleeve hasa plurality of macroscopic irregularities, the depth of which does notexceed half of the medium wall thickness of the sliding sleeve.

Likewise, it can be advantageous according to the invention if theinternal surface of the sliding sleeve has an average roughness depthR_(z) ranging from 5 μm to half of the average wall thickness of thesliding sleeve, preferably ranging from 10 μm to 2000 μm. The statedranges of the average roughness depth result in a well-balanced ratiobetween reduced force to be exerted for press-fitting and sufficientintrinsic elasticity of the sliding sleeve. The term “average roughnessdepth” (designated by the symbol “R_(z)”) of a surface means theroughness depth according to DIN EN ISO 4287/4288.

According to the present invention, preferred materials for theconnecting element are polymeric materials, such as, for example,polypropylene and glass fibre reinforced polypropylene, polyamides andglass fibre reinforced polyamides, temperature-resistant thermoplasticssuch as polyphenyl sulfone (PPSU), polyvinylidene fluoride (PVDF),polyether sulfone (PES), polyphenylene sulfide (PPS), polysulfone (PSU),acrylonitrile-butadiene-styrene (ABS) and polyester carbonate (PESC), aswell as copolymers and blends of such polymers, wherein said polymermaterials can also be used fibre reinforced, in particular glass fibrereinforced, as well as metallic materials, such as, for example, brass,in particular Ecobrass®, red brass and stainless steel.Temperature-resistant thermoplastics, such as polyphenyl sulfone andpolyvinyl fluoride, are particularly preferred for producing theconnecting element used according to the invention. The term“temperature-resistant thermoplastics”, as used herein, relates to theheat resistance and thermostability of this material group anddesignates thermoplastic polymer materials with a heat resistance attemperatures of at least 150° C. The upper limit of the temperature atwhich such temperature-resistant plastic can be used depends on thematerial used, wherein the usability of such polymer materials ends at amaximum of 260° C.

According to the present invention, used as plastic pipes areall-plastic pipes, preferably made of polyethylene (PE, in particular PE100 and PE-RT, cross-linked polyethylene (PE-X, in particular PE-Xa,PE-Xb and PE-Xc), polypropylene (in particular statistical polypropylenePP-R) and polybutylene (PB); as well as plastic composite pipes,preferably with layers of polyethylene (PE, in particular PE 100 andPE-RT), cross-linked polyethylene (PE-X, in particular PE-Xa, PE-Xb andPE-Xc), polypropylene (in particular statistical polypropylene PP-R)and/or polybutylene (PB). An additional layer of ethylene vinyl alcoholcopolymer (EVOH) may also be provided as oxygen barrier layer. Accordingto the present invention, metal-plastic composite pipes (MCV pipes)preferably comprise layers of polyethylene (PE, in particular PE 100 andPE-RT), cross-linked polyethylene (PE-X, in particular PE-Xa, PE-Xb andPE-Xc), polypropylene (in particular statistical polypropylene PP-R)and/or polybutylene (PB) and at least one layer of metals, preferablyaluminium. When using plastic composite pipes and MCV pipes, bondingagent layers may also be inserted between individual layers. Accordingto the present invention, all pipes in a pipe connection can beconstructed identically or one or more of the pipes can have differentstructures. In addition, the pipes can also be fibre reinforcedaccording to the present invention. The fibre reinforcement of the linepipes can be present in individual or all pipes, over the entire lengthof the pipe or only in sections as well. With regard to the plastic pipeor the metal-plastic composite pipe of the sliding sleeve connectionaccording to the invention, it is particularly preferable if at leastone layer of the respective pipe includes cross-linked polyethylene(PE-X, in particular PE-Xa, PE-Xb and PE-Xc). The material “cross-linkedpolyethylene” is a material that has a shape memory, a so-called “memoryeffect”. Such a memory effect means that the cross-linked polyethylenetries to return to its original shape after any change in its externalgeometry. During pipe expansion, this causes any pipe including PE-X totry to return to the original internal pipe diameter before theexpansion. As a support body of a connecting element is inserted in theexpanded end of the pipe after expansion, the memory effect when using apipe including at least one layer of cross-linked polyethylene leads toa particularly high tightness of the sliding sleeve connection accordingto the invention.

The connecting element of the sliding sleeve connection according to theinvention can be a threaded moulded part or a threadless moulded part,i.e. a connecting element with no thread. This in particular includesconnecting pieces, connection brackets, multiple distributors, t-pieces,wall t-pieces, wall brackets, system transitions, transition pieces,angled transition pieces, none of which have a thread. Accordingly, theterm “threaded moulded part” refers to a connecting element having atleast one threaded moulded part. This in particular includes connectingpieces, connection brackets, multiple distributors, t-pieces, wallt-pieces, wall brackets, system transitions, transition pieces andangled transition pieces, all of which have at least one internal and/orexternal thread.

According to the invention, the preferred materials for the slidingsleeve are those materials to which reference is made with relation tothe connecting element of the sliding sleeve connection according to theinvention. Temperature-resistant plastics and in particular polyphenylsulfone and polyvinylidene fluoride are particularly preferred asmaterials for the sliding sleeve. Cross-linked polyethylene (PE-X, inparticular PE-Xa, PE-Xb and PE-Xc) is also particularly preferred asmaterial for the sliding sleeve.

The sliding sleeve connection according to the present invention is inparticular used in piping and connection systems in drinking waterinstallation, in sprinkler systems, in radiator connections, in concretecore temperature controls as well as in surface heating or surfacecooling systems or even in fermenter heating devices or for theventilation of filter beds.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following is intended to explain the invention in detail withreference to the embodiments shown in the figures. The figures show in:

FIG. 1 a side view of a connecting element for use in a sliding sleeveconnection according to an embodiment of the present invention;

FIG. 2 is a side view of a sliding sleeve connection according to anembodiment of the present invention, in which a plastic pipe is slidonto a support body of the connecting element illustrated in FIG. 1,wherein the end of the pipe and the sliding sleeve are shown in section;and

FIG. 3 is a side view of a connecting element for use in a slidingsleeve connection according to a further embodiment of the presentinvention; and

FIG. 4 is a side view of a connecting element for use in a slidingsleeve connection according to a further embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a side view of a connecting element 1 for use in a slidingsleeve connection according to an embodiment of the present invention.The connecting element 1 is a connecting piece having two support bodies2, 2 a, wherein each of the support bodies 2, 2 a in the embodimentshown in FIG. 1 has three circumferential external ribs 3, 3 a, 3 b.Said three circumferential external ribs 3, 3 a, 3 b extend in an axialdirection, beginning at the open end of the connecting element 1, andare arranged in such a way that two consecutive saw-tooth-shapedcircumferential external ribs 3, 3 a are followed by a circumferentialexternal rib 3 b with a substantially rectangular cross section. Apre-stop 4, 4 a connects with each of the two support bodies 2, 2 a.Furthermore, the connecting element 1 has a circumferential collar 5, 5a for each support body 2, 2 a, which closes off the respective supportbody 2, 2 a.

The geometry of the connecting element 1 and the sliding sleeveconnection 6 according to the invention are described in detail in thefollowing with reference to the left support body 2 in FIG. 1, whereinit is understood that such explanations also apply to the right supportbody 2 a in FIG. 1 as well as to further existing support bodiespossibly present in other embodiments accordingly.

FIG. 2 shows a side view of an embodiment of a sliding sleeve connection6 according to the invention including the connecting element 1 shown inFIG. 1. A sliding sleeve 9, shown in a sectional view in FIG. 2, is slidtherein beyond the expanded end of the pipe 8 of the all-plastic ormetal-plastic composite pipe 7 slid onto supporting body 2 and extendingto the pre-stop 4 as a maximum, said pipe 7 also being shown insectional view in FIG. 2, in the direction of the circumferential collar5 of the connecting element. As the pre-stop 4 is spaced from thecircumferential collar 5, a hollow space is formed between the pre-stop4 and the circumferential collar 5. Said hollow space allows a bendingof the section of the sliding sleeve 9 protruding beyond the end of thepipe 8 in the direction of the supporting body 2. This results in amechanical fixing of the sliding sleeve 9 and thus an increasedstability of the sliding sleeve connection 6 according to the invention.In the embodiment of the connecting element 1 shown in FIG. 1 thedistance between the circumferential collar 5 of the connecting element1 and the associated pre-stop 4 is 0.20 times the length of the pipesupport body 2. In alternative embodiments of the connecting piece 1 thedistance between the pre-stop 4 and the circumferential collar 5 canequal 0.10 times to 0.50 times the length of the support body 2. As usedherein, the term “length of the support body 2” in each case refers tothe distance between the open end of the support body 2 of theconnecting element 1 and the circumferential collar 5. The externaldiameter of the pre-stop 4 in the embodiment of the connecting element 1shown is 1.25 times the external diameter of the circumferentialexternal ribs 3, 3 a, 3 b having the largest external diameter. Inalternative embodiments the external diameter of the pre-stop 4 canequal 1.1 times to 1.5 times the external diameter of thecircumferential external rib 3, 3 a, 3 b with the largest externaldiameter. If the external diameter of the pre-stop 4 is within thestated range, the pre-stop 4 constitutes a sufficiently large obstaclefor the expanded end of the pipe 8 without impairing the stability ofthe sliding sleeve connection 6 according to the invention. In theembodiment shown the ratio of the height of the pre-stop 4 over the basearea of the support body 2 to the wall thickness of the all-plastic ormetal-plastic composite pipe 7 is 0.75 and preferably ranges from 0.40to 1.0.

In the embodiment of the connecting element 1 shown in FIG. 1 and FIG. 2the distance between pre-stop 4 of the connecting element 1 and thenearest circumferential external rib 3 b to the latter is 0.2 times thelength of the support body 2. This allows the sliding sleeve 9 in thesliding sleeve connection 6 according to the invention to be pushed morestrongly into the expanded end of the pipe 8 of the all-plastic ormetal-plastic composite pipe slid onto the support body 2 than via thesection at which the circumferential external ribs 3, 3 a, 3 b arearranged (FIG. 2). This results in further increased stability of thesliding sleeve connection 6 according to the invention. In alternativeembodiments of the connecting piece 1 the distance between the pre-stop4 and the nearest circumferential external rib 3 b to the latter can be0.10 times to 0.50 times the length of the support body 2. The wallthickness or width of the circumferential collar 5 equals 0.11 times thelength of the support body 2, wherein in alternative embodiments of theconnecting piece 1 the width of the circumferential collar 5 can be0.050 times to 0.20 times the length of the pipe connection section.

The external diameter of the circumferential collar 5 is 1.4 times theexternal diameter of the circumferential external ribs 3, 3 a, 3 b,which have the same maximum external diameter in the embodiment shown.The risk of the press-fit tool slipping off the circumferential collar 5during pressing is thus low, thereby resulting in the resistance of thecircumferential collar. In alternative embodiments of the connectingpiece 1 the external diameter of the circumferential collar 5 is 1.0times to 2.0 times the external diameter of the circumferential externalrib 3, 3 a, 3 b with the largest external diameter. The length of thesupporting body 2 is 1.4 times the external diameter of thecircumferential external ribs 3, 3 a, 3 b, wherein in alternativeembodiments of the connecting piece 1 the length of the support body 2is 0.60 times to 2.0 times the external diameter of the circumferentialexternal rib 3, 3 a, 3 b with the largest external diameter. Theconnecting element 1 thus has good resilience to bending stress withreasonable material expense. The external diameter of thecircumferential external ribs 3, 3 a, 3 b measures 1.1 times theexternal diameter of the base area of the support body 2. This allowsthe circumferential external ribs 3, 3 a, 3 b of the connecting element1 in a sliding sleeve connection 6 according to the invention to bepushed far enough into the end of the pipe 8 slid onto the support body2 to ensure a secure and tight fit of the end of the pipe 8 on thesupporting body 2 with reasonable material expense. In alternativeembodiments of the connecting element 1 according to the invention themaximum external diameter of the circumferential external ribs 3, 3 a, 3b is 1.03 to 1.3 times the external diameter of the base area of thesupport body 2. Here, the circumferential external ribs 3, 3 a, 3 b canhave differing external diameters, although it is preferred that thecircumferential external ribs 3, 3 a, 3 b have the same externaldiameter. The distance between the two saw-tooth-shaped circumferentialexternal ribs 3, 3 a is 0.25 times the length of the support body 2,while the distance between the saw-tooth-shaped circumferential externalrib 3 a and circumferential external rib 3 b with a substantiallyrectangular cross-section is 0.2 times the length of the support body 2,always measured from the edges facing the circumferential collar. Thisallows the circumferential external ribs 3, 3 a, 3 b of the connectingelement 1 to be pressed far enough into the end of the pipe 8press-fitted onto the support body 2 to ensure a securely fitting seal.However, it is preferred if the three circumferential external ribs 3, 3a, 3 b are distributed as equally as possible on the correspondingsection of the support body 2. These advantages allow the distancebetween two circumferential external ribs 3, 3 a, 3 b in alternativeembodiments of the connecting element 1, always measured from the edgesfacing the circumferential collar, to equal 0.10 times to 0.50 times thelength of the support body 2 as well.

The connecting element 1 shown in FIG. 1 is designed in mirror symmetryto a level running down the middle between the two circumferentialcollars 5, 5 a and perpendicularly to the axis of the connecting element1. Accordingly, the comments made with reference to the support body 2thus apply analogously to support body 2 a.

The connecting element 1 in the embodiment shown in FIG. 1 is acomponent made of polyphenyl sulfone (PPSU). Also usable in alternativeembodiments of the connecting element 1 according to the invention arepolypropylene and glass fibre reinforced polypropylene, polyamides andglass fibre reinforced polyamides, polyvinylidene fluoride (PVDF),polyether sulfone (PES), polysulfone (PSU), polyphenyl sulphide (PPS),acrylonitrile-butadiene-styrene copolymer (ABS) and polyester carbonate(PESC), as well as copolymers and blends of said polymers, wherein saidpolymer materials can also be used fibre reinforced, in particular glassfibre reinforced, or metallic materials, such as brass, red brass andstainless steel.

Pipe 7 according to this embodiment of the present invention is anall-plastic pipe 7 made of cross-linked polyethylene (PE-X, inparticular PE-Xa, PE-Xb and PE-Xc). As an alternative, all-plastic pipesmade of other materials as well as plastic composite pipes andmetal-plastic composite pipe can also be used as pipe 7 in otherembodiments of the present invention. Preferred, however, when usingplastic composite pipes and metal-plastic composite pipes is a layer ofcross-linked polyethylene (PE-X), in particular PE-Xa, PE-Xb and PE-Xcas the layer facing the internal diameter of pipe 7.

A further pipe 7 can be connected to the second supporting body 2 aaccording to the invention by a sliding sleeve connection 6 according tothe invention. The further pipe 7 can have an identical or differentconstruction to the pipe 7 of the supporting body 2.

The inserted sliding sleeve 9 used to fix the expanded end of the pipe 8onto the supporting body 2 is a sleeve made of cross-linked polyethylene(PE-X, in particular PE-Xa, PE-Xb and PE-Xc) in the embodiment shown inFIG. 1, which has a constant cross-section over its entire length.Alternatively, sliding sleeves 9 made of other materials, in particularpolyvinylidene fluoride (PVDF), can also be advantageously used. Thesliding sleeve 9 in this embodiment has an internal surface with anaverage roughness value R_(a) in a range of 4 μm, wherein the roughnessof the internal surface in alternative embodiments of the sliding sleeve9 preferably ranges from 1 μm to half of the average wall thickness ofthe sliding sleeve 9. An increased roughness on the internal surface ofthe sliding sleeve 9, compared with sliding sleeves with smooth internalsurfaces, leads to a reduction in the force needing to be exerted foraxially sliding the corresponding sliding sleeve 9 onto the expanded endof the pipe 8 with inserted support body 2. At the same time, aninternal surface of the sliding sleeve 9 with increased roughness has alower tendency to relative motion of the sliding sleeve 9 on theexpanded end of the pipe 8, in particular in the event of thermalcycling.

In order to generate the sliding sleeve connection 6 according to theinvention, the sliding sleeve 9 is initially slid over the end 8 of theplastic pipe 7. An expansion tool is then inserted in the end of theplastic pipe 8 and the plastic pipe 7 is expanded at one end by means ofan expansion tool. Thereupon, the support body 2 of the connectingelement 1 is inserted in the expanded end 8 of the plastic pipe 7 untilthe expanded end 8 of the plastic pipe 7 is approximately attached tothe pre-stop 4. The expanded end 8 of the plastic pipe 7 contracts dueto the memory effect of the raw material, wherein the plastic materialof the plastic pipe 7 presses into the external contour of the supportbody 2 of the connecting element 1. The sliding sleeve 9 is then slid inan axial direction onto the expanded end 8 of the plastic pipe 7 withinserted support body 2 by a suitable press-fit tool in such a way thatthe expanded end 8 of the plastic pipe 7 is fixed on the support body 2.Further plastic pipes 7 or metal-plastic composite pipes 7 may now beconnected in the same way to further support bodies 2 a, thereby forminga sliding sleeve connection 6 according to the invention.

In the embodiment shown in FIG. 2, the expansion ratio is approximately0.25. This value is particularly preferred for a pipe connection 6between a connecting element 1 and an all-plastic pipe 7, while a valueof approximately 0.15 is particularly preferred for a connection betweena connecting element 1 and a metal-plastic composite pipe 2.

In turn, FIG. 3 shows a side view of a further preferred embodiment of aconnecting element 1 to form a sliding sleeve connection 6 according tothe invention. The connecting element according to FIG. 3 differs fromthe connecting element 1 shown in FIG. 1 merely due to the fact that thetwo pre-stops 4, 4 a are each connected with the associatedcircumferential collar 5, 5 a via bridges 10 formed thereon inone-piece. This results in a higher mechanical stability of theconnecting element 1. With regard to further properties of theconnecting element 1, as well as of the sliding sleeve connection 6formed therewith, the comments on FIG. 1 and FIG. 2 also apply to theconnecting element 1 according to FIG. 3.

FIG. 4 shows a side view of a connecting element 1 for forming aninventive sliding sleeve 6 according to a further preferred embodiment.The connecting element according to FIG. 4 differs from the connectingelement shown in FIG. 1 solely by the fact that each pre-stop 4, 4 a isconfigured attached to the associated circumferential collar 5, 5 a. Therespective pre-stop 4, 4 a thus forms an integral component of theassociated circumferential collar 5, 5 a. In this embodiment thepre-stop 4, 4 a and the associated circumferential collar 5, 5 a of asupporting body form a two-stage stepped arrangement. In this manner, itis achieved a higher mechanical stability of the connecting element 1.With regard to further properties of the connecting element 1, as wellas of the sliding sleeve connection 6 according to the inventiondesigned therewith, the comments on FIG. 1 and FIG. 2 also apply to theconnecting element 1 according to FIG. 4.

The connecting element 3 of the sliding sleeve connection 6 according tothe invention in the embodiments shown in FIG. 1, FIG. 2 and FIG. 3 is apipe connector with two pipe connection sections. Alternatively, theconnecting element 3 according to the invention can be configured as aconnecting piece, connection bracket, multiple distributor, t-piece,wall t-piece, wall bracket, system transition, transition piece andangled transition piece, each possibly designed with at least oneinternal and/or external thread or threadless.

The present invention has been described in detail with reference to theembodiments of the present invention shown in the illustrations. It isunderstood that the present invention is not limited to the embodimentsshown, but that the scope of the present invention results from theattached claims.

The invention claimed is:
 1. Sliding sleeve connection between anexpanded end of an all-plastic pipe or of a plastic composite pipe and aconnecting element, comprising: an expanded end of an all-plastic pipeor of a plastic composite pipe; a connecting element having at least onesupport body provided with circumferential external ribs, onto which theexpanded end of the all-plastic pipe or of the plastic composite pipe isslid, and at least one circumferential collar; and a sliding sleeve madeof elastically deformable polymer material axially slid onto theexpanded end of the pipe, wherein the sliding sleeve has a constantcross-section over its entire length at least before it is slid onto theexpanded end of the pipe, wherein the connecting element comprises apre-stop between the circumferential collar and the nearestcircumferential external rib to the latter, and the pre-stop constitutesa limitation for sliding onto the end of the pipe, wherein the pre-stopis spaced from the circumferential collar in a longitudinal direction ofthe connecting element to form at least one hollow space, the at leastone hollow space having a first circumferential wall formed by asidewall of the pre-stop and a second circumferential wall, parallel toand spaced from the first circumferential wall, formed by a sidewall ofthe circumferential collar, wherein an external diameter of the sidewallof the circumferential collar forming the second circumferential wall ofthe at least one hollow space is larger than an external diameter of thepre-stop, and wherein the end of the sliding sleeve facing thecircumferential collar protrudes beyond the end of the pre-stop facingthe circumferential external rib and bends into the at least one hollowspace.
 2. Sliding sleeve according to claim 1, wherein thecircumferential collar is connected with the pre-stop via a plurality ofbridges.
 3. Sliding sleeve connection according to claim 1, wherein thedistance between the edge of the pre-stop facing the circumferentialexternal ribs and the edge of the circumferential collar facing thepre-stop is 0.10 times to 0.30 times the length of the support body. 4.Sliding sleeve connection according to claim 1, wherein the externaldiameter of the pre-stop is 1.1 times to 1.5 times the external diameterof the circumferential external rib with the largest external diameter.5. Sliding sleeve connection according to claim 1, wherein at least oneof the circumferential external ribs has a saw tooth-like cross sectionand at least one of the circumferential external ribs has asubstantially rectangular cross section.
 6. Sliding sleeve connectionaccording to claim 1, wherein the distance between the edges of twoadjacent circumferential external ribs facing the collar is 0.10 timesto 0.50 times the length of the support body.
 7. Sliding sleeveconnection according to claim 1, wherein the external diameter of eachindependent circumferential external rib independently is 1.03 times to1.3 times the external diameter of the base surface of the support body.8. Sliding sleeve connection according to claim 1, wherein the width ofthe circumferential collar is 0.050 times to 0.20 times the length ofthe support body.
 9. Sliding sleeve connection according to claim 1,wherein the external diameter of the circumferential collar is 1.1 timesto 2.0 times the external diameter of the circumferential external ribswith the largest external diameter.
 10. Sliding sleeve connectionaccording to claim 1, wherein the distance between the pre-stop and thenearest circumferential external rib to the latter is 0.10 times to 0.50times the length of the support body.
 11. Sliding sleeve connectionaccording to claim 1, wherein the length of the support body is 0.60times to 2.0 times the external diameter of the circumferential externalrib with the largest external diameter.
 12. Sliding sleeve connectionaccording to claim 1, wherein the ratio of the height of the pre-stop tothe wall thickness of the pipe ranges from 0.40 to 1.0.
 13. Slidingsleeve connection according to claim 1, wherein the following applies tothe expansion ratio R(exp) of the sliding sleeve connection:0.05<R(exp)=[D(max)/D(internal)]−1<0.35 wherein D(max) stands for themaximum external diameter of the circumferential external ribs andD(internal) for the internal diameter of the pipe.
 14. Sliding sleeveconnection according to claim 13, wherein the pipe concerned is anall-plastic pipe and the expansion ratio R(exp) of the sliding sleeveconnection ranges from 0.10 to 0.35.
 15. Sliding sleeve connectionaccording to claim 13, wherein the pipe concerned is a metal-plasticcomposite pipe and the expansion ratio R(exp) of the sliding sleeveconnection ranges from 0.05 to 0.25.
 16. Sliding sleeve connectionaccording to claim 13, wherein the pipe concerned is an all-plastic pipeand the expansion ratio R(exp) of the sliding sleeve connection rangesfrom 0.15 to 0.25.
 17. Sliding sleeve connection according to claim 13,wherein the pipe concerned is a metal-plastic composite pipe and theexpansion ratio R(exp) of the sliding sleeve connection ranges from 0.10to 0.20.
 18. Sliding sleeve connection according to claim 1, wherein theinternal surface of the sliding sleeve has an average roughness value Raranging from 1 μm to half of the average wall thickness of the slidingsleeve.
 19. Sliding sleeve connection according to claim 1, wherein theinternal surface of the sliding sleeve has a plurality of macroscopicirregularities, the depth of which does not exceed half of the averagewall thickness of the sliding sleeve.
 20. Sliding sleeve according toclaim 1, wherein the circumferential collar is connected with thepre-stop via a plurality of bridges to form a plurality of hollow spacesseparated by the bridges circumferentially around the support bodybetween the pre-stop and the circumferential collar.
 21. Sliding sleeveaccording to claim 1, wherein a distance between the pre-stop and thecircumferential collar is 0.10 times to 0.50 times a length of thesupport body.
 22. Sliding sleeve connection according to claim 1,wherein the ratio of the height of the pre-stop to the wall thickness ofthe pipe ranges from 0.60 to 0.96.
 23. Sliding sleeve connectionaccording to claim 1, wherein the sliding sleeve is made of cross-linkedpolyethylene.